Radio-Frequency Identification (RFID) technology has become widely used in virtually every industry, including transportation, shipping, manufacturing, waste management, postal tracking, airline baggage reconciliation, and highway toll management. Recently, Wal*mart Stores, Inc. required that all shipments from its top one hundred suppliers are shipped with an RFID tag or label attached to each pallet or container, where the RFID tag or label carries information related to the shipment. RFID tags and labels are useful for tracking shipments from the supplier to the customer and even through the customer's supply chain.
A typical RFID system includes a plurality of RFID tags or labels, at least one RFID reader or detection system having an antenna for communication with the RFID tags or labels, and a computing device to control the RFID reader. An RFID tag typically does not include a layer of adhesive. An RFID label typically is an RFID tag having a layer of adhesive for attaching the RFID tag to an item. The RFID reader includes a transmitter that may provide energy or information to the tags or labels, and a receiver to receive identity and other information from the tags or labels. The computing device can read, and/or write, and processes the information obtained by the RFID reader.
In general, the information received from an RFID tag or label is specific to the particular application, but often provides an identification for an article to which the tag is affixed. Exemplary articles include manufactured items, shipping containers, books, files, animals, or virtually any other tangible article. Additional information may also be provided for the article. The tag or label may be used during a manufacturing process, for example, to indicate a paint color of an automobile chassis during manufacturing or other useful information.
The transmitter of the RFID reader outputs RF signals through the antenna to create an electromagnetic field that enables the tags or labels to return an RF signal carrying the information. The transmitter makes use of an amplifier to drive the antenna with a modulated output signal.
A conventional RFID tag or label may be an“active” tag or label that includes an internal power source, or a“passive” tag or label that is energized by the field created by the RFID reader antenna. Once energized, the tags and labels communicate using a pre-defined protocol, allowing the RFID reader to receive information from one or more tags or labels. The computing device serves as an information management system by receiving the information from the RFID reader and performing some action, such as updating a database. In addition, the computing device may serve as a mechanism for programming data into the tags or label via the transmitter.
A variety of methods of making RFID tags and circuits are known, including the following: U.S. Pat. No. 6,805,940; U.S. Pat. No. 6,816,125; U.S. Pat. No. 6,399,258; U.S. Publication No. 2003/0151028; U.S. Publication No. 2004/0175515; PCT Publication WO 03/038748; PCT Publication WO 00/42678; and U.S. Publication No. 2002/0018880.